1. Field of the Invention
This invention relates to a device for warning against possible occurrence of ESD (electrostatic discharge), and particularly a device of such type which may be worn on the wrist in a compact form.
2. Description of the Related Art
While the present invention is broadly useful for warning against possible occurrence of ESD from a charged body, the application of particular concern is the warning against possible damage to sensitive electronic devices due to the presence of static charges on the human body.
In the electronic industry, static electricity currently accounts for as much as $ 2 billion in damages to sensitive MOS devices each year. Most of these damages occur when MOS chips are touched by ungrounded personnel, due to the flow of static charges from the body to ground, through the circuits of the chip.
No device is currently available for warning against possible damage to sensitive MOS devices at the instant such damage is about to occur. It is the object of the present invention to provide such a device of compact and efficient character.
Apart from corporeal applications, a number of systems have been devised in the art to preclude static electricity build-up.
U.S. Pat. No. 3,634,726 issued Jan. 11, 1972 to Pierre Jay describes an apparatus for removing static electricity from plastic films.
U.S. Pat. No. 4,523,252 issued Jun. 11, 1985 to J. O. Wallen describes a device for eliminating static electricity on machines and charged materials.
U.S. Pat. No. 4,180,698 issued Dec. 25, 1979 to R. B. Carpenter describes a system for protection of objects located on the surface of the earth from the effects of atmospherics.
U.S. Pat. No. 4,766,903 issued Aug. 30, 1988 to Herbert Esper describes a device for detecting and removing static charges from the human body. The device, however, requires a ground connection.
U.S. Pat. No. 4,849,851 issued Jul. 18, 1989 to R. J. Cubbison, Jr. describes a static electric discharge device which may be contained in a wrist-mountable unit. The device is based on a concept that the electric field of the body can attract opposite charges from a layer of ionized air. The Cubbison, Jr. patent suffers various deficiencies in use, and will not achieve its intended purpose of effectively removing charges from the body, mainly due to the fact that the electric field at any particular point on the skin is negligibly small, since the charge is distributed all over the body.
The object of the present invention is to provide a device for producing an audible signal in the event that a charged person approaches a grounded or poorly grounded electronic device, thus warning against possible chip damage before the occurrence of such damage.